Breast carcinoma with chondroid differentiation: a clinicopathologic study of 21 triple negative (ER-, PR-, Her2/neu-) cases.

A total of 21 metaplastic breast carcinomas (MCs) with chondroid differentiation were evaluated to better establish the clinicopathological features of this variant. The tumors exhibited mainly invasive carcinoma admixed with areas of cartilaginous matrix production. An associated ductal intraepithelial neoplasia component grade 2 or 3 was observed in 43% of cases. Immunohistochemical analysis revealed a triple negative (ER-, PR-, and Her2/neu-) immunoprofile and no expression of the androgen receptor. EGFR-positivity was found in 88% of evaluated cases, consistent with the proposed basaloid phenotype for all MC. Compared with previous studies that reviewed MC with osseus and cartilaginous elements, the incidence of axillary lymph node metastasis was significantly higher in our study and 60% of positive nodes exhibited chondroid differentiation. Available follow-up data (n = 10) revealed aggressive behavior of this MC variant with frequent metastasis, including visceral involvement and local chest wall recurrence despite chemotherapy and radiation. Three patients subsequently died of metastatic disease.